Polypyrimidine/polypurine sequence in plasmid DNA enhances formation of dimer molecules in Escherichia coli. Dimerization of plasmid DNA in Escherichia coli.

Formation of dimer molecules of a recombinant plasmid, pTIR10, which carries a pyrimidine/purine-biased stretch occurs about 6-fold more efficiently than for the control plasmid pUC19 in Escherichia coli strain JM107. Since pyrimidine/purine-biased sequences have a potential to form unusual DNA structures, this observation suggests that the inserted sequence affects the replication process of plasmid DNA, probably by forming a triple helix under physiological conditions.